type NanoSecond = u64;
type Inch = u64;

#[allow(non_camel_case_types)]
type u64_t = u64;
fn main() {
    let ns: NanoSecond = 5 as u64_t;
    let inches: Inch = 2 as u64_t;
    // 别名不是新的类型
    println!("{} ns + {} inches = {} unit?", ns, inches, ns + inches);
}
